Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $46.64   3.854%   $48.4375   $48.44   $48.45   $48.40  
  Purchase #2 $150.52   10.182%   $165.8459   $165.85   $165.85   $165.80  
  Purchase #3 $9.26   3.476%   $9.5819   $9.58   $9.60   $9.60  
  Purchase #4 $195.57   8.467%   $212.1289   $212.13   $212.15   $212.10  
  Purchase #5 $66.67   12.661%   $75.1111   $75.11   $75.10   $75.10  
  Purchase #6 $71.55   10.233%   $78.8717   $78.87   $78.85   $78.90  
  Purchase #7 $188.44   7.314%   $202.2225   $202.22   $202.20   $202.20  
  7 purchase totals = $728.65       $792.1995   $792.20   $792.20   $792.10